Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$141.48	13.390%	$160.4242	$160.42	$160.40	$160.40
Purchase #2	$195.83	11.743%	$218.8263	$218.83	$218.85	$218.80
Purchase #3	$149.98	3.750%	$155.6043	$155.60	$155.60	$155.60
Purchase #4	$69.62	6.386%	$74.0659	$74.07	$74.05	$74.10
Purchase #5	$14.28	10.310%	$15.7523	$15.75	$15.75	$15.80
Purchase #6	$158.33	3.774%	$164.3054	$164.31	$164.30	$164.30
Purchase #7	$215.60	5.508%	$227.4752	$227.48	$227.50	$227.50
7 purchase totals =	$945.12		$1,016.4536	$1,016.46	$1,016.45	$1,016.50